1. Field of the Invention
The present invention relates to a back projection type transmission screen, with which images projected from a projector can be recognized from the side of the screen opposite to the projector side. The present invention relates to a transmission screen utilizing a special light diffusing layer and thereby exhibiting a sufficient viewing angle and superior transparency, through which background can be seen (see-through property).
2. Background Art
Most of the conventionally and practically used transmission screens use polarization films, fresnel lens sheets, lenticular lens sheets and so forth in order to obtain high luminance and high contrast. However, these conventional transmission screens are expensive, and it is substantially impossible to see the other side of the screens, because they use polarization films or lens sheets.
In show windows of stores, advertising representations are employed by sticking up posters, spray painting and so forth. However, such advertising representations are static, and unless sticking posters or giving painting again, the content of the advertisement does not change. Therefore, it is conceivable to project dynamic advertisements on show windows etc. by using a projector or the like. However, show windows etc. are highly transparent, and therefore projected light is transmitted through them without forming images. If a conventional transmission screen is stuck up on a show window, it becomes possible to see images projected from the back side. However, since conventional transmission screens are not transparent, it becomes impossible to see commercial advertising from the outside, and thus the show window becomes meaningless.
As a means for solving this problem, a transmission screen using a special transparent light scattering layer has been proposed, through which things behind can be seen, in Japanese Patent Unexamined Publication (KOKAI) No. 2001-242546.
However, although the transmission screen of Japanese Patent Unexamined Publication No. 2001-242546 shows sufficient transparency, it does not have a sufficient viewing angle, and images cannot be clearly recognized from a direction deviated from the front direction.